From the birth of the NFL in 1920 league titles were awarded to the team with the best winning percentage until 1932 when the Portsmouth Spartans, who would become the Detroit Lions two years later, tied for the league lead with the Chicago Bears.

The league decided a final game would be played in Chicago to decide that season’s champion. A severe blizzard and sub-zero cold forced the game from Wrigley Field to indoors at Chicago Stadium where approximately 11,000 fans showed up to watch the Bears beat the Spartans 9-0.

Because of that game rule changes were put in place for the 1933 season:

• The 10 team league was split into an Eastern and Western division with a championship game played between the two winners each year.

• In the most influential change to the game, forward passes would be allowed from anywhere behind the line of scrimmage instead of a passer needing to be five yards back before releasing the ball.

With these changes in place the 1933 season made a major advance towards being the game we watch today.

The importance of the league championship game changed for good after the 1970 AFL/NFL merger but up to that point there were some hard-fought, historic games played to crown each season’s champion. Here is a countdown of the ones that are the 10 greatest NFL/AFL championship games ever played.